Understanding Circuit Protection
Proper circuit breaker sizing is crucial for electrical safety and code compliance.
- Load Calculations Continuous load: 125% rating required. Motor FLA × 2.5 for startup. HVAC: 175% rating. General: 80% maximum load. Diversity factor: 0.6-0.8.
- Wire Sizing 14 AWG: 15A max. 12 AWG: 20A. 10 AWG: 30A. 8 AWG: 40A. 6 AWG: 55A. Temperature correction: 0.71-0.87 factor. Voltage drop: 3% maximum.
- Protection Types Standard: 15-200A. GFCI: 4-6mA trip. AFCI: arc detection. Dual Function: both protections. Selective coordination: 0.1-0.4s separation.
- Code Requirements NEC Article 240. UL 489 listed. Series rating allowed. Short circuit: 10kA minimum. AIC rating must exceed available fault current.
Installation Guide
Panel Requirements
Working space: 30"×36"×6'6". Dedicated circuits per NEC. AFCI: bedrooms required. GFCI: wet locations. Handle tie for multi-wire circuits.
Common Applications
Kitchen: 20A GFCI. Dryer: 30A 2-pole. Range: 40-50A 2-pole. HVAC: 20-60A. Subpanel: 60-100A. Main: 100-200A residential.
Cost Factors
Standard breaker: $5-15. GFCI: $35-50. AFCI: $40-60. Panel: $500-1500. Labor: $75-150/hr. Permit: $50-200. Testing: $100-300.
Maintenance Schedule
Test monthly: GFCI/AFCI. Annual thermal scan. Clean panel yearly. Exercise breakers: 6 months. Replace: 30-40 years. Log all trips.